Mercurial > repos > shellac > sam_consensus_v3
annotate env/lib/python3.9/site-packages/networkx/generators/tests/test_expanders.py @ 0:4f3585e2f14b draft default tip
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author | shellac |
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date | Mon, 22 Mar 2021 18:12:50 +0000 |
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1 """Unit tests for the :mod:`networkx.generators.expanders` module. |
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2 |
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3 """ |
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4 |
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5 import networkx as nx |
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6 from networkx import adjacency_matrix |
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7 from networkx import number_of_nodes |
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8 from networkx.generators.expanders import chordal_cycle_graph |
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9 from networkx.generators.expanders import margulis_gabber_galil_graph |
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10 from networkx.generators.expanders import paley_graph |
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11 |
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12 import pytest |
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13 |
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14 |
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15 def test_margulis_gabber_galil_graph(): |
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16 for n in 2, 3, 5, 6, 10: |
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17 g = margulis_gabber_galil_graph(n) |
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18 assert number_of_nodes(g) == n * n |
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19 for node in g: |
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20 assert g.degree(node) == 8 |
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21 assert len(node) == 2 |
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22 for i in node: |
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23 assert int(i) == i |
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24 assert 0 <= i < n |
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25 |
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26 np = pytest.importorskip("numpy") |
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27 scipy = pytest.importorskip("scipy") |
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28 scipy.linalg = pytest.importorskip("scipy.linalg") |
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29 # Eigenvalues are already sorted using the scipy eigvalsh, |
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30 # but the implementation in numpy does not guarantee order. |
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31 w = sorted(scipy.linalg.eigvalsh(adjacency_matrix(g).A)) |
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32 assert w[-2] < 5 * np.sqrt(2) |
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33 |
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34 |
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35 def test_chordal_cycle_graph(): |
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36 """Test for the :func:`networkx.chordal_cycle_graph` function.""" |
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37 primes = [3, 5, 7, 11] |
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38 for p in primes: |
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39 G = chordal_cycle_graph(p) |
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40 assert len(G) == p |
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41 # TODO The second largest eigenvalue should be smaller than a constant, |
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42 # independent of the number of nodes in the graph: |
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43 # |
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44 # eigs = sorted(scipy.linalg.eigvalsh(adjacency_matrix(G).A)) |
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45 # assert_less(eigs[-2], ...) |
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46 # |
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47 |
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48 |
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49 def test_paley_graph(): |
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50 """Test for the :func:`networkx.paley_graph` function.""" |
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51 primes = [3, 5, 7, 11, 13] |
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52 for p in primes: |
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53 G = paley_graph(p) |
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54 # G has p nodes |
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55 assert len(G) == p |
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56 # G is (p-1)/2-regular |
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57 in_degrees = {G.in_degree(node) for node in G.nodes} |
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58 out_degrees = {G.out_degree(node) for node in G.nodes} |
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59 assert len(in_degrees) == 1 and in_degrees.pop() == (p - 1) // 2 |
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60 assert len(out_degrees) == 1 and out_degrees.pop() == (p - 1) // 2 |
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61 |
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62 # If p = 1 mod 4, -1 is a square mod 4 and therefore the |
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63 # edge in the Paley graph are symmetric. |
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64 if p % 4 == 1: |
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65 for (u, v) in G.edges: |
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66 assert (v, u) in G.edges |
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67 |
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68 |
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69 def test_margulis_gabber_galil_graph_badinput(): |
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70 pytest.raises(nx.NetworkXError, margulis_gabber_galil_graph, 3, nx.DiGraph()) |
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71 pytest.raises(nx.NetworkXError, margulis_gabber_galil_graph, 3, nx.Graph()) |